Vessel having a control fin, for example, a keel or rudder, and mechanism for use therein

ABSTRACT

This invention relates to a vessel having a control fin which is fixed to or integral with a shaft rotatable about its longitudinal axis in a bearing attached to the vessel, the shaft being operable to rotate the fin through at least 100* in order to move it between an extended operating position and a retracted position in which the draught of the vessel is substantially reduced with respect to its maximum value, and in order to allow variation of the angle of attack of the fin.

United States Patent [1 1 S1bthorpe Dec. 4, 1973 VESSEL HAVING A CONTROL FIN, FOR 56] References Cited EXAMPLE, A KEEL OR RUDDER, AND UNITED S T PATENTS MECHANISM FOR USE THEREIN 1,703,868 3/1929 Chisholm, .lr 1 14/136 7 Inventor; Anthony sibthorpe, 24 Browning 3,226,738 1/1966 Fox 114/127 X Ave., Boscombe, Bournemouth, H hi E l d Primary ExaminerGeorge E. A. l-lalvosa Assistant ExaminerEdward R. Kazenske [22] 1971 Att0rneyWilliam Knoeller et al.

Appl. No.: 188,001

Foreign Application Priority Data Oct. 21, 1970 Great Britain 49,982/70 Jan. 25, 1971 Great Britain 3,105/71 Apr. 13, 1971 Great Britain 9,278/71 US. Cl 114/141, 114/136, 114/126 1111. c1 1363b 41/00 Field of Search 114/137, 136, 135,

[57] ABSTRACT This invention relates to a vessel having a control fin which is fixed to or integral with a shaft rotatable about its longitudinal axis in a bearing attached to the vessel, the shaft being operable to rotate the fin I through at least 100 in order to move it between an extended operating position and a retracted position in which the draught of the vessel is substantially reduced with respect to its maximum value, and in order to allow variation of the angle of attack of the fin.

4 Claims, 5 Drawing Figures VESSEL I-IAVING A CONTROL FIN, FOR EXAMPLE, A KEEL OR RUDDER, AND MECHANISM FOR USE THEREIN FIELD OF THE INVENTION This invention relates to a vessel having a control fin, for example a keel, rudder or hydrofoil. In thisspecification the term vessel is used to include hydrofoil craft and also air-cushion craft where these have one or more fins projecting into the water, and the terms draught, forward aft are used in the nauticalsense.

DESCRIPTION OF THE PRIOR ART A conventional vessel is often prevented from mooring in tidal waters by a central keel or by its rudder, which prevent it from resting stably on the mud. Such a vessel can also be prevented by a central keel or even by its r'udder from passing over shallows. This limits the mobility of the vessel.

Use of bilge keels has been proposed to alleviate these problems, but these involve a serious reduction in the windwardperformance of a sailing vessel. I

To partly alleviate these problems, it has also been proposed to provide vessels with centrally retractable keels, which can be raised in the vertical plane of the vessels. This involves sacrifice of valuable-cabin space. Moreover, the shape of the vessels hulls can still: prevent them from resting stably on the mud, and the rudders, although of a lesser draught than the keel, can still present difficulties.

SUMMARY OF THE INVENTION According to the present invention 1 provide a vesselv position in which the draught of the vesselis substantially reduced with respect to its maximum value, and in order to allow variation of the angle of attack of the fin.

Where the fin is a hydrofoil or rudder, the shaft is rotatable through an angle of less than 90 in order to change the angle of attack'of the tin.

a retracted position where the blade extends towards the vessel stern (front) with the blade will in a vertical plane. Preferably, the longitudinal axis of the rudder when in the retracted position is at an angle of between 80 and 100 relative to the position thereof when the rudder is in its extended position. This is useful to reduce the vesselsdraught at the stem. The rudder can be used in its retracted position by swinging the tiller 180 about a pivot in the head of the shaft, though its efficiency is less than when the blade is extended downwardly. Its effectiveness is sufficient for mooring manoeuvres. The shaft is disposed at an angle to the'axis of symmetry of the fin. In the case of a longitudinally extending fin, the shaft can be located in the plane of the fin (which will require a 180 rotation to fully reshaft by a pivotal connection so that the tiller can be In one embodiment, the fin is the keelof the vessel,

and the shaft is tilted forwardly and cantedlaterally of the vessels fore-and-aft vertical plane, in such a way that rotation of the shaft through 90 shiftsthekeel from its normal deep-water verticalorientationtoa retracted position in which the keelis disposedwithits plane substantially horizontal and spacedashorhdistance below the bottom of the vessel. In this form of the. invention, the keel is preferably designed so that its centre of gravity in the retracted position in which the keep is disposed with its plane substantially horizontal and spaced a short distance below the bottom of the vessel. In this form of the invention, the keel is preferably designed so that its centre of gravity in the retracted position lies in the fore-and-aft vertical plane of the vessel, thus reducing the outswinging ofthe centre -of% swung in a vertical plane through about 180 from its normal forwardly extending position to a reversed position in which it extends directly aft. If one then pulls the tiller substantially in a'horizontal plane (that is without swinging it) through 180 so that it again points forward, a rudder constructed according to the present invention will then have swunglikewise through 180 to a position where its length extends forwardly instead of downwardly, thereby reducing its draught. By choosing an appropriate angle between the shaft and the direction of the length of the blade, the rudder blade can be arranged to lie in this position with one edge along and close to the vessel keel band. The shaft is carried in one or more thrust bearings mounted in the vessel near to the keel.

A possible disadvantage of this arrangement is that the rudder exerts a large force on the tiller when manoeuvring forwardly in shallow water with the rudder blade retracted, that is raised, since the centre of lateral resistance of the immersed part of the blade is then forward of the shaft axis. Conditions are then similar to when manoeuvring in reverse with a conventional rudder.

I'nyet' another embodiment, the axis of the shaft lies in the plane of the rudder,-that area of the rudder in front of the axis being the leading area and that behind the axis being the'trailing-area. In this embodiment the rudder is constructed to ensure that the trailing area is greater than the leading area. For example, in the extended position the trailing area may'be substantially greater than the leading area. Thus, when the rudder is in:use in the extendedposition, a selflcentering effect is imparted to the rudder. The aspect ratio and the trailing and leading areas are selected in design so that when'the rudder is retracted, and pointing forwardly, the new leading area, vformerly'the trailing area, becomes less effective co rnpared to the new trailing area.

The newleading area then will not produce sufficient hydrodynamic force to dominate the new trailing area.

Thus a self-centering effect is again imparted to the rudder.

The invention also provides a vessel comprising a hull, a shaft'supported by said hull, a control fin fixed on one end of said shaft, and means for rotating the the shaft is rotated, in order to shift the control fin between an extended position for normal operation, and a retracted position for shallow water operation.

The invention further provides a vessel having a control fin which is fixed to or integral with a shaft rotatable about its longitudinal axis in a bearing attached to the vessel, the shaft being tilted forwardly and canted laterally of the vessels fore-and-aft vertical plane, in such a way that rotation of the shaft through 90 shifts the keel from its normal deep-water vertical orientation to a retracted position in which the keel is disposed with its plane substantially horizontal and spaced a short distance below the bottom of the vessel.

It is an object of this invention to provide a vessel which is not prevented from mooring in tidal .waters by its keel.

It is a further object of the invention to provide a vessel in which the keel can be retracted without substantial sacrifice of cabin space. I

It is a further object of the invention to provide a vessel having a rudder and keel which can both be retracted to reduce the draught of the vessel.

It is a further object of the invention to provide a vessel having at least one retractable fin whose angle of attack can be varied. It is yet a further object of this invention to permit the windward performance of a vessel to be improved and drift to leeward to be reduced by enabling the angle of attack of the keel to be varied.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the invention will become apparent from the accompanying drawings, in which:

FIGS. la to 1d illustrate a form of the invention-in which a vessel keel can be swung from the vertical to a horizontal position, FIG. 1d also showing how a control fin can be continuously adjusted in position in order to vary its angle of attack; and

FIG. 2 illustrates a part of a vessel and shows how the rudder may be swung between extended and retracted positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring firstly to FIGS. lb and 1d, a keel in its normal deep water position extends in a substantially vertical plane downwardly from the bottom of a boat 12. A faired casing 14 houses a mechanism for swinging the keel. A shaft 16 is fixed to the keel and extends into a thrust bearing 18 (FIG. lb) mounted in the-housing. As can be seen from the plan view FIG. 1a and the side elevation FIG. lb, the shaft is tilted forwardly and is canted transversely of the vertical central plane of the vessel. The shaft 16 carries a pinion 17 which engages a worm 19, the latter being connected via a rod or spindle to an operating handle 21. Thus operation of the handle 21 rotates the shaft 16 and swings the keel. Provision is preferably made for rotating the 'shaft 16 through a total of about 100, that is to say, 90 on one side of its normal central vertical position of the'keel and 10 on the other side thereof, for reasons that will be explained below. A lock 23 locks the keel in its extended position, and locks or catches may optionally be included to fix the keel in a slightly offset position for going to windward. The mechanism need not be manually operated; for larger vessels an electrical or mechanical drive or hydraulic ram may be used. Equally, mechanisms other than a worm-and-pinion could be employed. The shape of the keel I0 is chosen to that it matches closely with the faired casing 14 when fully extended and centrally disposed, see FIG. lb, and so that its centre of gravity lies on the vessel fore and aft central plane 20 (10a FIGS. la and 1c when fully re tracted. A stop 22 is fixed on the casing 14 to prevent bending of the keel when the boat rests on the sea bottom with the keel retracted. V

The right hand upper portion of FIG. 1d shows how a control fin extending laterally and downwardly outward from the hull of a vessel 72 can be retracted to a position 700 by rotating a shaft 74. The illustrated mechanism for turning the shaft 74 includes a pinion 76 and a worm 78. This mechanism allows an alteration of the angle of attack of the fin 70 during motion of the vessel, if this should be desirable, for example to improve windward performance.

The facility of varying the angle of attack of the keel permits the windward performance of a vessel to be improved; drift to leeward can be reduced or eliminated under suitable conditions. When the fin is a fin of a hydrofoil craft, the alteration of the angle of attack permits improvement of the lift and/or drag characteristics of the fin.

A rudder 110, illustrated in FIG. 2, is mounted at the stern of a vessel having a considerable overhang. The rudder is secured to a stock or shaft 112 which is mounted in thrust bearings 114 fixed to the vessel hull. The centre line of the rudder is at 45 to the shaft axis. The top end of the shaft 1 12 is joumalled in a stock casing 118, and is secured to a tiller by a pivotal connection 122. The connection 122 is such that the tiller 120 can be swung through in a vertical plane, when it is desired to retract the rudder. The axis of the stock 112, when the rudder is extended, passes through a point forward of the centre of lateral resistance of the immersed portion of the rudder 110.

' By swinging the tiller 120 through 180 in a vertical plane and then pulling it round in a horizontal plane to the illustrated position, the rudder 110 can be moved from the position illustrated in form lines to the position 110a illustrated in dotted lines. This results in a re-' duction in rudder depth which is useful for shallow water, especially when the vessel is equipped with a keel such as that illustrated in FIGS. la and lb.

The shaft 112 lies in the plane of the rudder. The shaft axis when projected passes through the forward edge of the rudder 110 at E. The comers of the rudder are designated A, B,.C and D. Area ADCE and area ABE are chosen to give a trailing effect to the rudder when it is in the extended (firm-line) position. The trailing effect causes the rudder to align itself with the direction of movement of the vessel.

The area ADCE is of greater area than ABE, and becomes inefi'ective compared to area ABE when the rudder is in its retracted position due to a change of the aspect ratio. Thus, in both the retracted and extended positions, the shape of the blade ensures that the rudder has the desired handling performance with noticeable self-centering effect.

The arrangement of the rudder illustrated in FIG. 2 is particularly satisfactory when correcting weatherhelm. This is because when the vessel is heeling to leeward, the movement of the rudder needed to correct weather-helm (namely tiller to windward) results in the rudder biting deeper into the water.

The invention in its broader aspects is not limited to i the specific embodiments described but departures may be made therefrom in the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

I claim:

1. A vessel having a hull, a bearing attached to the hull, a shaft rotatable about its longitudinal axis in the bearing, a keel which is fixed to or integral with the shaft, the shaft being tilted forwardly and canted laterally of the vessels fore-and-aft vertical plane, in such a way that rotation of the shaft through 90 shifts the keel from its normal deep-water vertical orientation to a retracted position in which the keel is disposed with its plane substantially horizontal and spaced a short distance below the bottom of the vessel.

2. The vessel of claim 1, further comprising a faired casing, and a mechanism in said casing for rotating said shaft.

3. The vessel of claim 2, wherein said mechanism comprises a worm and a pinionl 4. The vessel of claim 3, further comprising lock means to lock said keel in its extended position. 

1. A vessel having a hull, a bearing attached to the hull, a shaft rotatable about its longitudinal axis in the bearing, a keel which is fixed to or integral with the shaft, the shaft being tilted forwardly and canted laterally of the vessel''s foreand-aft vertical plane, in such a way that rotation of the shaft through 90* shifts the keel from its normal deep-water vertical orientation to a retracted position in which the keel is disposed with its plane substantially horizontal and spaced a short distance below the bottom of the vessel.
 2. The vessel of claim 1, further comprising a faired casing, and a mechanism in said casing for rotating said shaft.
 3. The vessel of claim 2, wherein said mechanism comprises a worm and a pinion.
 4. The vessel of claim 3, further comprising lock means to lock said keel in its extended position. 